• Title, Summary, Keyword: Rotor dynamics

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Review of Balancing Techniques for Rotor (회전분의 발란싱기술에 관한 고찰)

  • Kim, Yeong-Ju
    • 한국기계연구소 소보
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    • pp.143-161
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    • 1984
  • The mass balancing of rotors is an integral part of the study practice of the rotor dynamics. Any machine with rotating components is considered to be rotating machine. The part of a rotating machine that rotates in normal operation is generally reffered to as a rotor. A rotor is flexible if it deforms when the machine is operating at any speed up to its maximum design speed. Otherwise, the rotor is rigid. The general Purpose of the study of rotor dynamics is to increase understanding of rotor vibration phenomena and thus provide a means for controlling or eliminating these vitrations. As the efficiency of rotating machinery has been increased through reduced weight and increased speed, which implies increasement of rotor flexibility, the control of rotor vibration has become essential. Thus, the study and practice of rotor dynamaics has taken on an increasingly important role in recent years. Therefore many workers have studied about this and introduced a few balancing methods of flexible rotor, which can be classified mainly in following four sorts, 1. Polar plotting methed 2. Modal balancing method 3. Influence coefficient method 4. Unified balancing approach In this paper practical theories of rotor dynamics related to flexible rotor balancing have been reviewed and confirmed the calculation results of flexible balancing of typical rotor, as an example, respectively

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A study on the nonlinear normal modes of rotors (회전체의 비선형 정규 모우드에 관한 연구)

  • 김용철
    • Journal of Ocean Engineering and Technology
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    • v.10 no.1
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    • pp.17-24
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    • 1996
  • In the present paper nonlinear normal modes of a rotor system is studied. The methodology to obtain the nonlinear normal modes is based on center manifold reduction technique. It also provides a way of nonlinear coordinate transform from the physical cordinates to the modal coordinates and an idea of individual nonlinear modal dynamics. In order to apply the present method to a rotor dynamics a single mass rotor system on nonlinear elastic supports is employed and the nonlinear normal modes of the system are obtained.

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Design and Analysis of Permanent Magnet Synchronous Generator Considering Magnetically Coupled Turbine-Rotor System

  • Kim, Byung-Ok;Choi, Bum-Seog;Kim, Jeong-Man;Cho, Han-Wook
    • Journal of Electrical Engineering and Technology
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    • v.10 no.3
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    • pp.1002-1006
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    • 2015
  • In this paper, design and analysis of permanent magnet synchronous generator for ocean thermal energy conversion (OTEC) considering magnetically coupled turbine-rotor system is discussed. In particular, the rotor dynamics considering bearing span and journal shaft diameter is highlighted. The two topologies of permanent magnet synchronous generator with magnetic coupling are employed for comparison of computed rotor dynamics and generating characteristics. The analysis results show that the critical speed of the turbine-rotor system is higher when the rotor is coupled by magnetically coupling. Finally, the experimental results confirmed the validity of the proposed design and analysis scheme and successful development.

A study on the Modeling for Rotors Control with Dynamics Analysis S/W (동역학 S/W와 연계한 회전체 제어의 모델링에 관한 연구)

  • Lee W.C.;Kim S.W.;Kim J.S.;Park H.O.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.906-909
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    • 2005
  • This study provides the method to build the rotor system model using dynamic analysis software. also, it introduces the traditional methods of the rotor system modeling and informs the each merits and demerits. We will make up the flexible system of rotor system model with ADAMS, multi-body dynamics S/W, in order to develop dynamics model and get the response of plant model near to real model through connection the SIMULINK of MATLAB. We will develop the computing dynamics-controling model possible controlled simulation similar to a real model with controlling the plant model.

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Two Plane Balancing Method based on the Equations of Motion of Rotor Dynamic System (회전체 동역학계의 운동방정식에 근거한 양면 밸런싱 기법)

  • Jeong, Dong-Hwa;Park, No-Gil
    • Proceedings of the KSME Conference
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    • pp.623-628
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    • 2000
  • Since the influence coefficients method in balancing of rotors is developed with the basement of not the principle of rotor system dynamics, but the linear relationshop of between the measuring quantities and the unbalance quantities, field engineers can apply the method without additional understanding on the rotor dynamics. But the influence coefficients method is not robust to the measurement error. This paper proposes a new method for the two plane balancing of rigid rotor, based on the principle of rotor dynamics. And the kit for experiment is made by ourselves, and in order to measure in the same condition with it, we do a experiment three times. And then with the Response of gap sensor, the SNR(Signal and Noise) is compared and analyzed about measuring error between the influence coefficient method, and the new method, and it is proved that the new method is less robust than the influence coefficient method.

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Adaptive Wavelet Analysis of Non-Stationary Vibration Signal in Rotor Dynamics

  • Ji Guoyi;Park Dong-Keun;Chung Won-Jee;Lee Choon-Man
    • International Journal of Precision Engineering and Manufacturing
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    • v.6 no.4
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    • pp.26-30
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    • 2005
  • A rotor run-up or run-down process provide more useful information for modal analysis than normal operation conditions. A traditional difficulty associated with rotor run-up or run-down analysis is the non-stationary nature of vibration data. This paper compares Short-Time Fourier Transform (STFT) and the wavelets analysis in these non-stationary signal analyses. An Adaptive Wavelet Analysis (AWT) is proposed to analyze these signals. Although simulations and experiments in a simple rotor-bearing system show that both STFT and AWT can be used to analyze non-stationary vibration signals in rotor dynamics, proposed AWT provides better results than STFT analysis. From the amplitude-frequency curve obtained by AWT, the modal frequency and damping ratio are calculated. This paper also analyzes the characteristics of signals when the shaft touches the outer hoop in a run-up process. The AWT can give a good result in this complex dynamic analysis of the touching process.

A Study on the Identification and Robust Control of Flexible Rotor Supported by Magnetic Bearing (자기베어링으로 지지되는 연성축계의 식별 및 강인 제어에 관한 연구)

  • Ahn, H. J.;Jeon, S.;Han, D. C.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.3-6
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    • 2000
  • The magnetic bearing system are intrinsically unstable, and need the feedback control of electromagnetic forces with measured displacements. So the controller design plays an important role in constructing high performance magnetic bearing system. In case of magnetic bearing system, the order of identified model is high because of unknown dynamics included in closed loop systems - such as sensor dynamics, actuator dynamics - and non-linearity of magnetic bearings itself. In this paper the identification and robust control of flexible rotor supported by magnetic bearing are discussed. We measure and identify overall system that contains not only flexible rotor model but also magnetic bearing and time delay. The structured and unstructured uncertainties are modeled that cover variations of natural frequencies, uncertainties in sensor and actuator gains and unmodeled dynamics. And desired performances are specified with several weighting function. Using augmented system that includes identified model, uncertainties, and weighting functions, μ-synthesis is applied to flexible rotor supported with magnetic bearing. The flexible rotor was spin up over the first flexible critical speed.

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Papers : Implicit Formulation of Rotor Aeromechanic Equations for Helicopter Flight Simulation (논문 : 헬리콥터 비행 시뮬레이션을 위한 로터운동방정식 유도)

  • Kim, Chang-Ju
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.3
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    • pp.8-16
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    • 2002
  • The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.

Study on Vertical Dynamics Compensation for Wobbling Effect Mitigation of Electrostatically Levitated Gyroscope

  • Lee, Jongmin;Song, Hyungmin;Sung, Sangkyung;Kim, Chang Joo;Lee, Sangwoo
    • International Journal of Aeronautical and Space Sciences
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    • v.15 no.3
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    • pp.293-301
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    • 2014
  • We present a study of vertical dynamics control of an electrostatically levitated gyro-accelerometer considering the wobbling effect and propose a tilt stabilization method with newly introduced control electrodes. Typically, a rotor in a vacuum rotates at high velocity, which may create a drift rate and lead to displacement instability due to the tilt angle of the rotor. To analyze this, first we set up a vertical dynamic equation and determined simulation results regarding displacement control. After deriving an equation for drift dynamics, we analyzed the drift rate of the rotor and the wobbling effect for displacement control quantitatively. Then, we designed new sub-electrodes for moment control that will decrease the drift amplitude of wobbling dynamics. Finally, a simulation study demonstrated that the vertical displacement control with the wobbling compensation electrodes mitigated the rotor's drift rate, showing the effectiveness of the newly proposed control electrodes.

Optimization and dynamic characteristics of the hybrid type vacuum pump (하이브리드 타입 진공펌프의 동특성 및 최적화)

  • Kim, Yong-Hwi;Lee, Jong-Myeong;Ahn, Byeong-Hyun;Ha, Jeong-Min;Choi, Byeong-Keun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.306-310
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    • 2014
  • The purpose of this study is the stability evaluation of a vacuum pump through modal test and rotor dynamics. Eigenvalue was solved by the finite-element method(FEM) using 2D and 3D models, then the modal test result was compared with the FEM result. According to the comparison, the analysis result using the 2D was more accurate than the 3D model. Therefore, rotor dynamics was performed by the 2D model. Campbell diagram and root-locus maps, which were calculated by complex-eigenvalue analysis, were used to evaluate the stability of the rotors of the vacuum pump. And displacement solved by unbalance response analysis was compared with the minimum clearance between two rotors of the vacuum pump. Thus, the vacuum pump is assumed operated under steady state through the evaluation of the rotor dynamics.

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